OCaml evaluator for page dispatch + handler aser, 83/83 Playwright tests

Major architectural change: page function dispatch and handler execution
now go through the OCaml kernel instead of the Python bootstrapped evaluator.

OCaml integration:
- Page dispatch: bridge.eval() evaluates SX URL expressions (geography, marshes, etc.)
- Handler aser: bridge.aser() serializes handler responses as SX wire format
- _ensure_components loads all .sx files into OCaml kernel (spec, web adapter, handlers)
- defhandler/defpage registered as no-op special forms so handler files load
- helper IO primitive dispatches to Python page helpers + IO handlers
- ok-raw response format for SX wire format (no double-escaping)
- Natural list serialization in eval (no (list ...) wrapper)
- Clean pipe: _read_until_ok always sends io-response on error

SX adapter (aser):
- scope-emit!/scope-peek aliases to avoid CEK special form conflict
- aser-fragment/aser-call: strings starting with "(" pass through unserialized
- Registered cond-scheme?, is-else-clause?, primitive?, get-primitive in kernel
- random-int, parse-int as kernel primitives; json-encode, into via IO bridge

Handler migration:
- All IO calls converted to (helper "name" args...) pattern
- request-arg, request-form, state-get, state-set!, now, component-source etc.
- Fixed bare (effect ...) in island bodies leaking disposer functions as text
- Fixed lower-case → lower, ~search-results → ~examples/search-results

Reactive islands:
- sx-hydrate-islands called after client-side navigation swap
- force-dispose-islands-in for outerHTML swaps (clears hydration markers)
- clear-processed! platform primitive for re-hydration

Content restructuring:
- Design, event bridge, named stores, phase 2 consolidated into reactive overview
- Marshes split into overview + 5 example sub-pages
- Nav links use sx-get/sx-target for client-side navigation

Playwright test suite (sx/tests/test_demos.py):
- 83 tests covering hypermedia demos, reactive islands, marshes, spec explorer
- Server-side rendering, handler interactions, island hydration, navigation

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

sx/sxc/pages/docs.sx

@@ -369,17 +369,11 @@
   :path "/language/specs/explore/<slug>"
   :auth :public
   :layout :sx-docs
+  :data (helper "spec-explorer-data-by-slug" slug)
   :content (~layouts/doc :path (str "/sx/(language.(spec.(explore." slug ")))")
-    (let ((spec (find-spec slug)))
-      (if spec
-        (let ((data (spec-explorer-data
-                      (get spec "filename")
-                      (get spec "title")
-                      (get spec "desc"))))
-          (if data
-            (~specs-explorer/spec-explorer-content :data data)
-            (~specs/not-found :slug slug)))
-        (~specs/not-found :slug slug)))))
+    (if data
+      (~specs-explorer/spec-explorer-content :data data)
+      (~specs/not-found :slug slug))))
 
 ;; ---------------------------------------------------------------------------
 ;; Bootstrappers section